jtlan

[MOCs] GE 23-ton boxcabs (head-to-head with CommanderWolf)

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After the last boxcab, Commander Wolf and I figured we had to go smaller.

And slower.

So we decided that both of us should build a motorized model of a GE 23-ton boxcab. We agreed to build them models independently, then meet up and compare approaches.

We started with the same scaling image:

scaling_drawing.jpg

Since there was some variation among the prototypes, choice of details was a matter of taste. I took most of my references from here. Here's my finished model:

img_0721.jpg

The original locomotive is really tiny, so I tried to keep the model about 7 studs wide. There's a lot of SNOT in this model: The main chassis is upside-down, the deckplate and frames are held against that using Technic pins, and the body attaches to some jumpers on the deckplate:

z_exploded.png

The battery box is mounted sideways in the body and the power switch is reached by jabbing an antenna through the window. The roof is actually only held on by gravity:

img_0726.jpg

Originally I wasn't sure if I was going to put the caution-stripe tiles on the frames, but codefox421 vouched for them.

You can see the full Brickshelf gallery here.

So, what did Commander Wolf do? Read on...

Edited by jtlan

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Ahem, yes, mine is black because I'll build in any color as long as it's black.

img_0810.jpg

The biggest driver behind my design was that I wanted to keep the battery box upright and the switch easily accessible.

img_0811.jpg

To that end, the final result is probably mediocre. The roof isn't studded onto anything and comes on and off easily enough, but as you can see it doesn't sit quite flush with the top of the body when the switch isn't depressed.

img_0813.jpg

It's also considerably wider because I thought it was important to have a perceptible outward step between the body and the frame and a perceptible inward step between the frame and the chassis.

img_0814.jpg

This is probably the part I'm least happy with: the sides are held on by those fence pieces down at the chassis, and everything lines up really nicely in LDD, but in practice the walls tend to cave in and out a little and don't line up perfectly with the front and back walls.

img_0815.jpg

And you can see that we both decided to use the same drivetrain. And because of that, you can see that both locos travel at exactly the same speed, as shown in the following video:

That's all my pics, so there is no full gallery. Til next time!

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I couldn't believe that the micromotor can move the boxcab, let alone anything else. Really cool!

The micromotor is probably geared down alot to make it turn so slowly, and thus it does have significant torque for its size. A bigger difficulty was actually transferring that torque to the wheels because you have to stick something with a hole (rather than a crossaxle hole) onto the end of the micromotor. We both independently experimented with belt drives at first and deemed it insufficient because power wasn't being transferred uniformly.

Edited by Commander Wolf

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They're cute! I love seeing the old-school parts like the micro-motor and the 1x4 fences being used.

That must be the slowest Lego train video ever though....

How long do they run on a full battery?

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Hi JTLan and Commander Wolf,

First, these builds are totally cool! I got really excited when I saw how little space the battery, motor, and driving gears had been crammed into. I've been working on 6-wide designs, so fitting batteries and motors gets tight. I didn't even know the micro-motor exists.

But then I looked up the micro-motor on Brick Link and it looks like it's $20 for just the motor, used but known working, vs $13 for a brand new power functions powered truck.

It looks to me like maybe the big win here is the ability to build a powered truck with tighter wheel spacing. I built a mock-up of the moving parts for a faux Boeing-Vertol LRV but the Power Functions motor has the wheels spaced too far apart.

Two questions:

- Can the Power Functions IR receiver be placed between the old 9V battery box and the 9V micro-motor, or would I need to use a "real" power-functions battery box?

- How well does the speed of a pair of micro-motors track? I'm thinking about a truck with only one powered axle, but two powered trucks in the vehicle; that way the wheels could be very tightly spaced.

Thanks!

Ben

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- Can the Power Functions IR receiver be placed between the old 9V battery box and the 9V micro-motor, or would I need to use a "real" power-functions battery box?

Yes it can. However the connectors of 9V and PF don't match. From receiver to motor is no problem, the converter cable (https://www.bricklink.com/catalogItem.asp?P=60656)works fine.

The problem is that you can't use the same cable to connect the battery box so you'll have to make up your own cable.

One hack that I found a long time ago (can't remember where) is to connect the battery box to one output of the receiver. It works but it's not efficient; you're losing power that way. There's an explanation in the comments on this photo:

8078349348_8f800e33d6_z.jpg

PF with old 9V by Duq, on Flickr

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- Can the Power Functions IR receiver be placed between the old 9V battery box and the 9V micro-motor, or would I need to use a "real" power-functions battery box?

- How well does the speed of a pair of micro-motors track? I'm thinking about a truck with only one powered axle, but two powered trucks in the vehicle; that way the wheels could be very tightly spaced.

To the first point I think custom cables are the way to go. It's not hard to do and the PF cables are pretty cheap. I'm not actually sure you're "losing power" with the hack Duq posted, but I haven't studied the wiring too carefully on the PF stuff. jtlan could tell you more.

To the second point we looked at 3 or 4 used micromotors and we've found they can vary quite a bit in performance. Presumably if you got two brand new ones they should be the same, but we didn't look at that. Either way if you have enough weight on the bogies and the wheels have enough traction it should even out the performance. I wouldn't worry too much about this second point in general.

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Yes it can. However the connectors of 9V and PF don't match. From receiver to motor is no problem, the converter cable (https://www.bricklin...tem.asp?P=60656)works fine.

The problem is that you can't use the same cable to connect the battery box so you'll have to make up your own cable.

One hack that I found a long time ago (can't remember where) is to connect the battery box to one output of the receiver. It works but it's not efficient; you're losing power that way. There's an explanation in the comments on this photo:

8078349348_8f800e33d6_z.jpg

PF with old 9V by Duq, on Flickr

In this image it looks like you could disconnect the converter cable from the output of the receiver and put the receiver input on top of the converter that is on the battery box...does that work?

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In this image it looks like you could disconnect the converter cable from the output of the receiver and put the receiver input on top of the converter that is on the battery box...does that work?

That won't work; the converter cable only passes the C1/C2 control lines, and not the +9V/0V power lines:

pfcon.jpg

(Image from Philo's page on PF).

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Fantastic models! And I love Living in a Box. One of my all time favorite songs...

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